Irritable bowel syndrome (IBS) is a long-term and episodic medical disorder shown to have an impact on work productivity and health-related quality of life (QOL). The objective of this study was to assess the impact of IBS on work productivity and on health-related QOL in an employed population in the United States and to quantify the cost of these factors to the employer. A 2-phase survey was sent to the workforce of a large US bank to assess the presence of IBS among employees and to measure their work productivity (absenteeism [time lost from work] and presenteeism [reduced productivity at work]) and health-related QOL. Forty-one percent of the 1776 employees responding to both phases of the survey met the Rome II criteria for IBS. Employees with IBS reported a 15% greater loss in work productivity because of gastrointestinal symptoms than employees without IBS and had significantly lower Medical Outcomes Study Short Form 36 (SF-36) scores than those without IBS. IBS was associated with a 21% reduction in work productivity, equivalent to working less than 4 days in a 5-day workweek. Employees with IBS also had significantly lower scores on all domains of the SF-36, indicating poorer functional outcomes. Reduced work productivity and diminished QOL of these magnitudes may have substantial financial impact on employers.

(Am J Manag Care. 2005;11:S17-S26)

Patients with irritable bowel syndrome (IBS) report symptoms that may wax and wane in type and severity over time1,2 and that can have a negative impact on health-related quality of life (QOL).3-6 IBS affects adults of all ages, primarily those of working age (30-50 years old).2 In the United States, an estimated 10% to 20% of adults are believed to have symptoms consistent with this disorder.3

Although estimates of the direct costs associated with IBS are staggering and can vary greatly,7 the impact of IBS on absenteeism (hours absent from work), presenteeism (reduced productivity while at work), and health-related QOL is of increasing concern to employers in the United States, who rely heavily on a healthy workforce and who contract with health plans and other payers to cover the healthcare costs of their employees. For these reasons, employers often implement wellness and disease management programs to optimize workforce health.

Leong and colleagues8 studied healthcare insurance data of the employees of a self-insured Fortune 100 company and determined that direct and indirect costs for patients with IBS were substantially greater than those for a matched non-IBS control group. In 1998, the direct and indirect medical costs to the employer for 1 employee with IBS were $3997 and $2367, respectively, which were $1651 and $468 greater than the direct and indirect medical costs for 1 employee without IBS. The indirect cost for patients with IBS is likely to have been underestimated, however, because this estimate included absenteeism but not presenteeism.

Hahn and colleagues9 measured the impact of IBS on absenteeism. Although the actual number of hours employees were absent from work because of IBS was not substantial, the number of missed workdays increased significantly as the severity of illness increased. In a separate study of IBS patients, Hahn and colleagues10 found that Medical Outcomes Study Short Form 36 (SF-36) scores of respondents from the United States and the United Kingdom were significantly lower, meaning that they were worse than the respective population norms. Moreover, 30% of US respondents missed at least 1 full day of work in the 4 weeks preceding the survey, and 46% reported "cutting back" on some workdays because of IBS.

Although several studies have reported reduced health-related QOL in IBS populations, 3-6 limited research has been conducted to assess health-related QOL or absenteeism in an employed population with IBS, and even less research has been conducted to quantify the economic impact of these factors on the employer. Additionally, these studies have largely ignored the specific impact of IBS-associated gastrointestinal (GI) symptoms on presenteeism.

Our objective was to assess the impact of IBS on work productivity (presenteeism and absenteeism) and on health-related QOL in a US employed population and to quantify the cost of these factors to the employer.

Methods

Participants were employees of Comerica Incorporated, a nationwide bank with major branches in multiple states (Michigan, California, Texas, and Florida). From April 2002 to August 2002, all employees of Comerica (N = 11 806) were invited to participate in a 2-phase survey regarding GI health and related symptoms.

All Comerica employees were mailed a survey designed to (1) identify those with IBS (including subgroup classification for constipation [IBS-C] or diarrhea [IBS-D]) using the Rome II criteria11-13; (2) measure the frequency, severity, and bothersomeness of IBS symptoms; and (3) capture information on sociodemographics, long-term health conditions (including physician-diagnosed IBS), and job characteristics. A postcard was included in the initial mailing to request signed consent for participation in the followup survey. Employees who completed initial surveys and consent forms received a second survey measuring work productivity loss because of IBS and assessing QOL (Figure 1). The Cedars-Sinai Health System Institutional Review Board approved this study.

Names of initial survey participants were entered in a raffle for 1 of 9 gift checks valued between $100 and $500. Second-phase survey participants received a gift check for $25. All participants received educational material regarding IBS at the conclusion of the study.

Rome II Criteria. Employees were administered the Rome II diagnostic criteria questionnaire11-13 to assess the presence of IBS. According to the Rome II criteria, IBS is defined by the presence of abdominal discomfort or pain for at least 12 weeks, which need not be consecutive, during the preceding 12 months, and the discomfort or pain should have 2 of the following 3 features: it should be relieved with defecation; its onset should be associated with a change in the frequency of the stool; its onset should be associated with a change in the form (appearance) of the stool.13 Supportive symptoms can be used to classify IBS patients into symptom subgroups: IBS-C, characterized by less than 3 stools per week, hard/lumpy stools, straining, and feeling of incomplete bowel evacuation; IBS-D, characterized by more than 3 stools per week, loose or watery stools, and urgency; and mixed-pattern subtypes (alternating IBS).13,14

Assessment of Work Productivity. Work productivity was measured using the Work Productivity and Activity Impairment (WPAI) questionnaire,15 which was developed and validated as a general health measure that can be easily modified for specific health conditions. Adapted versions of the WPAI16 have been developed for use in patients with conditions such as allergy,16,17 long-term hand dermatitis,18 and gastroesophageal reflux disease (GERD).19,20 We adapted the WPAI to estimate the impact of GI symptoms consistent with IBS, including abdominal pain or discomfort, bloating, and constipation or diarrhea, on work productivity.16 Areas assessed included level of impairment during work and other daily activities and hours absent from work because of IBS symptoms during the previous 7 days. A scale from 0 to 10 was used to assess the degree to which GI symptoms consistent with IBS negatively affected a patient's productivity while working and to assess how they affected daily activity. Measures of productivity and absenteeism were combined in the work productivity score (WPS), which quantifies reduced work productivity (absenteeism and presenteeism) attributed to GI symptoms consistent with IBS as a percentage of potential total work productivity during a full-time workweek. The WPS was calculated as follows:

WPAI measures are interpreted as a percentage reduction in productivity (or a percentage of productivity lost) and are adjusted for part-time status. For example, a WPS of 5% indicates that a full-time employee is working at only 95% of full work potential (eg, 40 hours) because of reductions associated with absenteeism and presenteeism. A WPS of 5% for an employee working 40 hours per week would imply a reduction of 2 hours of potential work productivity lost.

Medical Outcomes Study Short Form. QOL was assessed using the SF-36 questionnaire, a generic instrument designed to measure overall health status.21,22 The WPS = [(hours absent from work + percentage of reduced productivity at work × hours actually worked)/(hours missed because of ill health + hours worked)] × 100. SF-36, which has previously been validated for use in the measurement of health-related QOL among IBS patients,23 assesses health status across 8 subscales, including physical functioning, physical role limitations, emotional role limitations, social functioning, bodily pain, general mental health, vitality, and general health perceptions. Additionally, subscale scores can be collapsed into 2 summary scores, the mental component summary (MCS) and the physical component summary (PCS).24 Scores for each subscale and summary score range from 0 (poor health) to 100 (optimal health).

Statistical Analysis. Employees meeting the Rome II criteria for IBS were compared with those not meeting the criteria with respect to a variety of variables, including demographic and work-related measures, presence of comorbid conditions, and history of hysterectomy or surgeries of the GI tract. Chi-square tests were used for categorical variables and t tests for continuous variables. Two-sided P values were calculated, and statistical significance was set at the &#954;= 0.05 level.

The kappa coefficient was calculated to assess the agreement between respondents meeting the Rome II criteria (based on the questionnaire) and respondents indicating a diagnosis of IBS by a physician or another medical professional (formal diagnosis). The kappa statistic describes the degree of agreement between 2 variables. Kappa values range between -1.0 (perfect disagreement) and +1.0 (perfect agreement), with zero indicating agreement that is completely accounted for by chance. Values of 0.0 to 0.2 indicate slight agreement, 0.2 to 0.4 fair agreement, 0.4 to 0.6 moderate agreement, 0.6 to 0.8 substantial agreement, and 0.8 to 1.0 near-perfect agreement.

Employees with and without IBS (as determined by their having met the Rome II criteria) were compared with respect to mean percentage reductions across WPAI measures of productivity, and a similar comparison was made between IBS-C and IBS-D subgroups. A nonparametric method, bootstrapping, was used to estimate the 95% confidence interval (CI) for differences in productivity impairments. Bootstrapping is a statistical approach for estimating CIs from data simulations when distributions deviate considerably from the assumptions of parametric statistics. Mean percentage reductions in WPAI measures of productivity were converted to lost work productivity based on total number of hours absent from work (absenteeism) and total number of hours at reduced productivity while at work (presenteeism) based on a 40-hour workweek (using the WPS formula presented in this article). These hours were also quantified based on the mean salary and mean wages of employees in the sample. The mean cost in dollars of reduced work productivity (absenteeism and presenteeism) per year (assuming full-time employment of 2080 hours of potential work time annually per employee) because of GI symptoms consistent with IBS was calculated as the difference in cost of reduced work productivity between employees with and without IBS. The cost per employee was extrapolated to a company with 10 000 employees assuming IBS prevalence estimates ranging from 10% to 20%.

Health-related QOL scores were calculated for the MCS and PCS and for each of the 8 SF-36 subscales. Mean differences in scores between IBS and non-IBS groups and between IBS-C and IBS-D subgroups were calculated with 95% CI.

Results

Survey participation is outlined in Figure 1. The initial survey was sent to all 11 806 Comerica employees and was returned by 2615 (22.2%) employees. Compared with the general Comerica employee population, respondents were similar in age, sex, and work status (full-time vs part-time). Completed surveys along with consent forms were submitted by 2276 (87.0%) employees, who then received the phase 2 survey; that survey was completed by 1776 (78.0%) of the initial respondents. The 1776 phase 2 respondents were similar to the 500 phase 2 nonrespondents in age, sex, education, compensation type (salary vs hourly wage), and work status (full-time vs part-time) (P >.05 for each). However, those who completed the survey were more likely to be white (P = .0002).

Patient Characteristics. Among the 1776 phase 2 respondents, 720 (40.5%) employees met Rome II criteria for IBS. Of these, 191 (27%) and 255 (35%) met Rome II IBS subtype criteria for IBS-C and IBS-D, respectively; the remaining 38% reported mixed-pattern bowel habit. Employees with IBS were similar to those without IBS (n = 1056) in age, compensation type (salary vs hourly wage), and work status (full-time vs part-time) (P >.05 for each) (Table 1). Employees with IBS were more likely to be women (P <.0001) (man/woman ratio, 1:5.1), were less likely to have a graduate degree (P = .03), and differed slightly with regard to race and ethnicity (P = .04). Employees with IBS were also more likely to have allergies, anxiety, depression, GERD, stomach ulcers, gallstones, and incontinence than employees without IBS (P <.001 for each).

Symptoms of abdominal pain or discomfort, diarrhea, constipation, gas, and bloating were each significantly more frequent and severe among employees with IBS than among those without IBS (P <.05). In addition, the IBS group reported greater levels of distress (moderate to extreme) because of each of the above symptoms than the group without IBS (P <.05). The greatest differences in reported frequency of symptoms between employees with and without IBS were for abdominal pain or discomfort and bloating, whereas the greatest reported differences in distress were attributed to the symptoms of constipation, diarrhea, and bloating. Exploratory and excisional surgeries associated with abdominal pain or symptoms were significantly more common among employees with IBS (Table 2), as were other types of surgery, such as appendectomy, cholecystectomy, and hysterectomy (P <.05). Small bowel resection and obstruction were more common among employees with IBS (P = .06).

Agreement Between Rome II Criteria and Professional Diagnosis of IBS. Data from the initial survey responders (n = 2615) were used to assess agreement between employees meeting Rome II symptom criteria (n = 1042) and those reporting a previous diagnosis of IBS determined by a physician or another medical professional (n = 269) (Figure 2). Agreement between a diagnosis of IBS by a physician or a medical professional and a diagnosis of IBS using the Rome II criteria was low (&#954;= 0.22), indicating that most patients whose IBS was diagnosed using the Rome II criteria had not been previously diagnosed by a physician or a medical professional. Among employees reporting a previous diagnosis of IBS by a physician or another medical professional, 86% (n = 230) met Rome II criteria; in comparison, of the 2346 employees who did not report a diagnosis of IBS by a physician or a medical professional, 35% (n = 812) met Rome II criteria. Thus, the Rome II captured most of the IBS diagnoses previously made by a physician or another medical professional, and it was also able to capture a significant number of IBS cases that had not yet been formally diagnosed. Of the total number of respondents who met Rome II criteria during the initial survey (n = 1042), 22% (n = 230) also reported IBS previously diagnosed by a physician or another medical professional, whereas only 2% (n = 39) of employees not meeting the Rome II criteria for IBS (n = 1573) reported a physician or a medical professional diagnosis of IBS. Thus, the proportion of diagnoses by a physician or a medical professional that were not identified using the Rome II criteria was small.

Impact of IBS on Work Productivity. Figure 3 provides measures of work productivity (absenteeism and presenteeism) and activity impairment for employees with and without IBS. Among employees with IBS, productivity at work (presenteeism) was reduced by more than 21% because of GI symptoms consistent with IBS; this figure was 15% (95% CI, 13.4-16.6) higher than that reported among employees without IBS. The percentages of work time missed (absenteeism) were 1.7% and 0.4% (mean percentage difference, 1.3; 95% CI, 0.7-1.9) among those with and without IBS, respectively.

The largest contributor to total productivity loss, WPS, was reduced productivity at work (presenteeism) (15%; 95% CI, 13-17). In comparison, absenteeism contributed only slightly to the total WPS (1.3%; 95% CI, 0.7-1.9). GI symptoms consistent with IBS were associated with a 21.1% reduction in total WPS among employees with IBS compared with a 6.1% reduction among those without IBS. Reductions in total WPS among employees with IBS-C and IBS-D were comparable at 18.2% and 20.8%, respectively. Based on the average hourly wage of each employee, reduction in total WPS resulted in average losses of $10 884 and $3147 for employees with and without IBS, respectively. Thus, the value of work productivity loss per individual because of IBS-attributable GI symptoms was $7737 (95% CI, $7332-$8143) per year.

Employees with IBS reported a mean reduction of nearly 27% in regular daily activities (ie, work around the house, shopping, childcare, exercising, studying) because of GI symptoms consistent with IBS. This accounted for the largest difference between IBS and non-IBS employees, as shown by a 19% (95% CI, 16.9-20.7) mean difference in daily activity impairment.

Impact of Work Productivity Reduction on the Employer. The incremental work productivity loss associated with IBS represents an additional 39 days of reduced productivity at work and an additional 3.4 days of absence per year for each employee with IBS. Assuming participants are representative of the Comerica employee population (10 000 employees) and assuming a 10% prevalence of IBS, the employer loses a total of $7 737 600 per year. If the prevalence of IBS is 20%, the resultant work productivity loss increases to $15 475 200 per year. Among salaried employees with IBS (n = 481), mean work productivity losses attributable to GI symptoms consistent with IBS ranged from 19% to 21%, regardless of salary range ($15 000-$35 000, $35 000-$55 000, $55 000-$80 000, and >$80 000). In contrast, hourly employees with IBS earning &#8804;$15 per hour (n = 155) experienced a 44% greater work productivity loss than those with IBS earning >$15 per hour (n = 100) (26% vs 18% work productivity loss for &#8804;$15 per hour vs >$15 per hour, respectively).

Impact of IBS on Health-related QOL. Scores for all SF-36 subscales were significantly lower for employees with IBS than for those without IBS (P <.05) (Figure 4). The most significant difference was in physical role limitations, with a mean difference of 24.6 (95% CI, 21.4-27.7) points between employees with and employees without IBS. Compared with subjects with IBS-D, those with IBS-C scored lower on the MCS and reported greater impairment on 6 of 8 SF-36 domains (although only emotional role functioning was statistically significant).

MCS and PCS scores were lower among employees with IBS than among those with- out IBS, with mean differences of 5.9 (95% CI, 5.0-6.9) and 5.4 (95% CI, 4.7-6.0), respectively.

Discussion

IBS is a long-term and episodic disorder, with GI symptoms (abdominal pain or discomfort and bloating associated with altered bowel function) that can wax and wane and that affect many persons during their most productive years of adulthood. This study is one of the first evaluations performed in a US employed population that measure the impact of IBS on work productivity and on health-related QOL. We found that IBS is significantly associated with reduced work productivity and that it significantly impacts health-related QOL, suggesting that management strategies targeting improvements in symptoms consistent with IBS and health-related QOL should be expected to have a positive impact on work productivity.

Reduced productivity while at work (presenteeism) because of GI symptoms consistent with IBS was a major contributor to total reduced work productivity. Employees with IBS experienced an additional 15% reduction in work productivity beyond that reported among controls. For an employee who works 40 hours per week, this 15% difference amounts to another 6 hours of work productivity lost per week. Although reduced work productivity resulting from GI symptoms amounts to approximately 15.8 days per year for employees without IBS, it accounts for more than 54.8 days per year for employees with IBS.

The largest component of total productivity reduction in employees with IBS was impairment while working. Absenteeism because of GI symptoms consistent with IBS contributed less to reductions in work productivity in this population. Absenteeism was low among all participants—1.7% and 0.4% among those with and without IBS, respectively (Figure 3), corresponding to approximately 3 hours per month of absence among employees with IBS and less than 1 hour per month of absence for non-IBS employees. Although studies have reported higher average absenteeism rates of 1 to 2 days per month, they have assessed absenteeism from all causes, not just GI symptoms.9,25

The impact of IBS on absenteeism and presenteeism observed in this study may impose a substantial financial burden on employers. It is possible that this study has underestimated the work productivity loss—a previous study using objective measures of productivity among employees from a large US credit card company found that mean total time lost per month from presenteeism, absenteeism, and disability for employees with digestive disorders was equivalent to more than twice the hours per month of work productivity loss measured in the present study.26 Few data are available to compare subjective (self-report) and objective measures of productivity, but the validation studies of the Work Limitations Questionnaire and the WPAI suggest that estimates based on self-reported data are valid.15,27

Our findings on overall work impairment in employees with IBS (21%) are comparable with those previously reported for other GI disorders, such as GERD (16%-35%).19,20 Overall work impairment was also comparable with that for other health conditions, including chronic hand dermatitis (17%)18 and allergic rhinitis (23%-42%),28 in studies that used the WPAI.

Employees with IBS had SF-36 scores within the range of scores reported for other long-term health conditions, such as back pain, ulcer, osteoarthritis, and congestive heart failure,29 and were comparable with previous measurements of health-related QOL in IBS populations.3-5

There are limitations to this observational study. As with all surveys, there is a risk for selection bias, particularly given the 22% response rate. Although low, this response rate is consistent with rates seen in other employer-based studies (20%-50%).30-34 The study cover letter sent to employees indicated that the study dealt with GI symptoms, a disclosure required by the employer and the institutional review board. It is possible that employees with symptoms were more likely to participate, leading to an overrepresentation of IBS patients in the study population. The similarity between employees with and without IBS along demographic and workrelated variables suggests that study results were unlikely to have been biased by differences in these variables. The banking industry employs a disproportionate number of women, but the ratio of women to men with IBS in our study was approximately 1.5:1—similar to proportions observed in other epidemiologic studies of IBS.25,35,36 Additionally, treatment for IBS symptoms may influence the degree of reduced work productivity. However, we were unable to explore the percentages of reduced work productivity among IBS patients being treated compared with those who had not sought care, because we did not question employees regarding their current treatments.

Our results indicate that IBS significantly affects work productivity. Further studies are required to better assess this impact in more defined populations of IBS, such as those seeking or receiving medical care, and in other employed populations. In addition, there is a need to better understand the determinants of work productivity losses in IBS and the relationship between direct medical costs and indirect costs (absenteeism and presenteeism). Finally, from an employer's perspective, additional efforts are needed to ensure that patients are identified and offered appropriate treatment because unique therapeutic agents can decrease symptom severity and frequency while improving employee health-related QOL and work productivity. Such efforts could pay dividends in the form of improved productivity and reduced absenteeism.

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